The present invention relates, in general, to electronics, and more particularly, to power supply controllers including semiconductors devices for power supplies and methods of forming such semiconductor devices.
In the past, the electronics industry utilized various methods and structures to form an illumination system for image capturing devices such as still image cameras and motion video cameras. Advances in digital technology allowed merging of still image capturing and motion video capturing into a single image capturing device. For example, cellular telephones progressed to include the ability to capture a single image as a still picture or to capture continuous motion has a movie or motion video. In order to provide the ability to operate in low light situations, these image capturing devices also included a method of illuminating the subject to be captured. A xenon light source generally was utilized to provide a pulsed flash in order to capture a single still image. A xenon light source was used because the xenon light source provided a high intensity light. However, the xenon light source was not suitable for continuous illumination that was required for continuous motion video. As a result, a second light source, typically a light emitting diode (LED), was used to provide a continuous light source for the continuous motion video.
The xenon light source required a high voltage pulse, typically about two hundred fifty to three hundred twenty volts (250-320 V), in order to energize the xenon light source to produce a pulse or flash of light. Conversely, the LED utilized a lower voltage source that can be supplied for a longer period of time. Consequently, the still image section included a complete power supply to operate the xenon light source and the video section included another complete power supply to operate the LED. As a result, the illumination system usually included a complete power supply including a switching power supply controller and an inductor, such as a transformer, for the still image section and another complete power supply including another switching power supply controller and another inductor, such as another transformer, for the video section. Having two complete power supply systems with two power supply controllers and two inductors increased the cost of the image capturing device.
Accordingly is desirable to have a power supply system for the illumination section of an image capturing device that does not require two inductors or two transformers, that does not required two separate switching power supply controllers, and that has a lower cost.
For simplicity and clarity of the illustration, elements in the figures are not necessarily to scale, and the same reference numbers in different figures denote the same elements. Additionally, descriptions and details of well-known steps and elements are omitted for simplicity of the description. As used herein current carrying electrode means an element of a device that carries current through the device such as a source or a drain of an MOS transistor or an emitter or a collector of a bipolar transistor or a cathode or anode of a diode, and a control electrode means an element of the device that controls current through the device such as a gate of an MOS transistor or a base of a bipolar transistor. Although the devices are explained herein as certain N-channel or P-Channel devices, or certain N-type or P-type doped regions, a person of ordinary skill in the art will appreciate that complementary devices are also possible in accordance with the present invention. It will be appreciated by those skilled in the art that the words during, while, and when as used herein relating to circuit operation are not exact terms that mean an action takes place instantly upon an initiating action but that there may be some small but reasonable delay, such as a propagation delay, between the reaction that is initiated by the initial action. The use of the word approximately or substantially means that a value of an element has a parameter that is expected to be very close to a stated value or position. However, as is well known in the art there are always minor variances that prevent the values or positions from being exactly as stated. It is well established in the art that variances of up to at least ten percent (10%) (and up to twenty percent (20%) for semiconductor doping concentrations) are reasonable variances from the ideal goal of exactly as described.